Transfer apparatus and transfer method

ABSTRACT

A transfer apparatus for performing transmission and reception of data using a plurality of lanes includes: a transmission control unit configured to, upon receiving a transmission instruction for performing a data transfer in a redundant mode in which the same data is transferred using a plurality of lanes, output transmission data as first data and second data without renegotiation with another transfer apparatus; a first transmission unit configured to transmit the first data output by the transmission control unit via a first lane; and a second transmission unit configured to transmit the second data output by the transmission control unit via a second lane.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority of theprior Japanese Patent Application No. 2018-16691, filed on Feb. 1, 2018,the entire contents of which are incorporated herein by reference.

FIELD

Embodiments discussed herein are related to a transfer apparatus and atransfer method.

BACKGROUND

In recent years, a serial transmission method has been used for theinterconnection between integrated circuits between which data transferis performed. The serial transmission method is a method ofsuperimposing a clock and data on each other in a single signal andtransmitting the signal. A multi-lane serial transmission method inwhich a plurality of serial transmissions are set as a group realizes awide frequency band.

In the multi-lane serial transmission, a transmission side distributesdata among a plurality of lanes as bit strings. Each of the lanestransmits a bit string using a clock. A reception side reproduces aclock from a signal received from each lane and reads out a bit stringfrom the received signal using the reproduced clock. In addition, thereception side corrects the skew of a transmission delay between lanesand restores original data from the bit strings in the lanes.

The distribution of data among a plurality of lanes and the restorationof data from the lanes are usually performed by a physical codingsublayer in a physical layer. A physical layer accommodates thedifference between transmission media, so that an upper layer in thephysical layer may perform multi-lane serial transmission withoutdepending on the transmission media.

In the multi-lane serial transmission, for the increase in availability,negotiation regarding a transmission speed and a lane to be used isperformed at the time of initialization. For the purpose of faulttolerance and power saving, a data transfer is temporarily suspendedduring operation and renegotiation is performed.

In a case where multi-lane serial transmission is performed under severetransmission conditions, an error rate in the multi-lane serialtransmission increases under the influence of environmental conditionssuch as power supply quality and temperatures. An upper layer detects agenerated error and corrects the error by retransmitting data. However,in a case where the error rate is high, the transfer of the data is notsuccessfully performed even though retransmission is repeated. The upperlayer diagnoses the unsuccessful data transfer as a failure in theserial transmission. Renegotiation is performed and the detection andisolation of a lane whose transmission quality has deteriorated areperformed. As a result, the multi-lane serial transmission iscontinuously performed.

There is a serial attached SCSI (SAS) expander that isolates a fault byautomatically detecting faulty communication in one of links anddisabling a PHY connected to the link where the faulty communication hasbeen detected.

There is a failover technique for, when detecting a fault in a firstlink that connects a first PCI bridge and a first IO device, using theunused portion of a second link that connects a second PCI bridge and asecond IO device as an alternative to the first link.

Related arts are disclosed in Japanese National Publication ofInternational Patent Application No. 2009-540436 and Japanese Laid-openPatent Publication No. 2012-118969.

SUMMARY

According to an aspect of the embodiments, a transfer apparatus forperforming transmission and reception of data using a plurality of lanesincludes: a transmission control unit configured to, upon receiving atransmission instruction for performing a data transfer in a redundantmode in which the same data is transferred using a plurality of lanes,output transmission data as first data and second data withoutrenegotiation with another transfer apparatus; a first transmission unitconfigured to transmit the first data output by the transmission controlunit via a first lane; and a second transmission unit configured totransmit the second data output by the transmission control unit via asecond lane.

The object and advantages of the invention will be realized and attainedby means of the elements and combinations particularly pointed out inthe claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and arenot restrictive of the invention.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a diagram describing a distribution mode;

FIG. 1B is a diagram describing a nonredundant mode;

FIG. 1C is a diagram describing a redundant mode;

FIG. 2 is a functional block diagram of a media access control unit in atransmission apparatus according to an embodiment;

FIG. 3 is a functional block diagram of a media access control unit in areceiving apparatus according to an embodiment;

FIG. 4 is a flowchart illustrating a process performed by a media accesscontrol unit in a transmission apparatus; and

FIG. 5 is a flowchart illustrating a process performed by a media accesscontrol unit in a receiving apparatus.

DESCRIPTION OF EMBODIMENTS

A prior art for performing renegotiation to detect and isolate a lanewhose transmission quality has deteriorated is useful when thetransmission quality of a specific lane continuously deteriorates.However, in a situation where the transmission qualities of a pluralityof lanes alternately deteriorate, a problem arises where time-consumingrenegotiation is frequently performed and a data transfer is notperformed during the renegotiation.

It is an object of the present disclosure to address the situation wherethe transmission qualities of a plurality of lanes alternatelydeteriorate without suspending a data transfer.

A transfer apparatus and a transfer method according to an embodiment ofthe present disclosure will be described in detail below with referenceto the accompanying drawings. It is to be noted that the followingembodiments do not limit the disclosed technique.

Embodiments

First, three transfer modes according to an embodiment will bedescribed. The three transfer modes are a distribution mode, anonredundant mode, and a redundant mode. FIG. 1 A is a diagramdescribing the distribution mode. FIG. 1B is a diagram describing thenonredundant mode. FIG. 1C is a diagram describing the redundant mode. Acase where the number of lanes is two will be described in embodiments.However, the number of lanes may be three or more. Examples of amulti-lane serial transmission include Ethernet (registered trademark),a universal serial bus (USB), and a peripheral component interconnect(PCI).

In the distribution mode, as illustrated in FIG. 1A, upon receivingtransmission data “ABCDEFGH” input from an upper layer, atransmission-side media access control unit 1 a adds #N and CRC to thetransmission data and distributes the transmission data to respectivelanes in units of characters. Here, #N represents the serial number oftransmission data and CRC represents a cyclic redundancy check (CRC)code to be used for error detection. Referring to FIG. 1A, #N and “ACEG”are distributed to a left lane and “BDFH” and CRC are distributed to aright lane.

A transmission-side physical unit 1 b in each lane adds anidentification code (Start) to the head of the distributed data, adds anidentification code (End) to the tail of the distributed data, andtransmits the data to a serial transmission line as a bit string. Areception-side physical unit 2 b in each lane recognizes identificationcodes in a received bit string and extracts distribution data.

A reception-side media access control unit 2 a couples #N and “ACEG”received by the left lane and “BDFH” and CRC received by the right laneand checks #N and CRC. When #N indicates the serial number of data to bereceived next and there is no CRC error, the reception-side media accesscontrol unit 2 a outputs the coupled received data “ABCDEFGH” to anupper layer.

In the nonredundant mode, as illustrated in FIG. 1B, data is transferredby only one of two lanes. Upon receiving transmission data “ABCDEFGH”input from an upper layer, the transmission-side media access controlunit 1 a adds #N and CRC to the transmission data and transmits thetransmission data to the physical unit 1 b in the left lane.

The transmission-side physical unit 1 b in the left lane addsidentification codes to the head and tail of the data and transmits thedata to a serial transmission line as a bit string. It is assumed thatthe right lane has been determined to have bad transmission quality andhas been isolated at the time of negotiation.

The reception-side physical unit 2 b in the left lane recognizesidentification codes from a received bit string, extracts #N,“ABCDEFGH”, and CRC from the received bit string, and transmits them tothe reception-side media access control unit 2 a. The reception-sidemedia access control unit 2 a checks #N and CRC and outputs “ABCDEFGH”to an upper layer when #N indicates the serial number of data to bereceived next and there is no CRC error.

In the redundant mode, as illustrated in FIG. 1C, the same data istransferred to two lanes. Upon receiving transmission data “ABCDEFGH”input from an upper layer, the transmission-side media access controlunit 1 a adds #N and CRC to the transmission data and transmits thetransmission data to both of the physical units 1 b in the left andright lanes. Each of the physical units 1 b in the left and right lanesadds identification codes to the head and tail of the data and transmitsthe data to a serial transmission line as a bit string.

Each of the physical units 2 b in the left and right lanes recognizesidentification codes from a received bit string, extracts #N,“ABCDEFGH”, and CRC from the bit string, and transmits them to thereception-side media access control unit 2 a. It is assumed that data inthe left lane includes an error.

The reception-side media access control unit 2 a performs a CRC checkupon received data in the left lane, detects an error, and removes theerror. In addition, the reception-side media access control unit 2 achecks #N and CRC in received data in the right line, checks that #Nindicates the serial number of data to be received next and there is noCRC error, and outputs data “ABCDEFGH” received by the right lane to anupper layer.

Thus, in the redundant mode, the reception-side media access controlunit 2 a outputs received data to an upper layer when an error is notfound in any one of the left and right lanes. The switching from thedistribution mode to the redundant mode is performed withoutrenegotiation. Accordingly, in a data transfer according to anembodiment, the situation where the transmission qualities of the leftand right lanes alternately deteriorate may be addressed withoutrenegotiation.

Next, the configuration of the media access control unit 1 a in atransmission apparatus according to an embodiment and the configurationof the media access control unit 2 a in a receiving apparatus accordingto an embodiment will be described. FIG. 2 is a functional block diagramof the media access control unit 1 a in a transmission apparatusaccording to an embodiment. FIG. 3 is a functional block diagram of themedia access control unit 2 a in a receiving apparatus according to anembodiment.

As illustrated in FIG. 2, the media access control unit 1 a in atransmission apparatus 1 includes an upper portion transmissioninterface 11, a transmission processing circuit 12, and two mediaindependent interface transmission blocks 13.

The upper portion transmission interface 11 receives transmission datafrom the upper portion (upper layer) of the transmission apparatus 1 andtransmits the transmission data to the transmission processing circuit12.

The transmission processing circuit 12 transmits the transmission datato the two media independent interface transmission blocks 13 in atransmission mode (transfer mode) specified by the upper portion. In acase where the transmission mode specified by the upper portion is thedistribution mode, the transmission processing circuit 12 distributesthe transmission data between the two media independent interfacetransmission blocks 13. The transmission processing circuit 12 transmitsa serial number to one of the media independent interface transmissionblocks 13 and transmits CRC to the other one of the media independentinterface transmission blocks 13.

In a case where the transmission mode specified by the upper portion isthe nonredundant mode, the transmission processing circuit 12 transmitsa serial number, transmission data, and CRC to the media independentinterface transmission block 13 determined at the time of negotiation.In a case where the transmission mode specified by the upper portion isthe redundant mode, the transmission processing circuit 12 transmits aserial number, transmission data, and CRC to both of the mediaindependent interface transmission blocks 13.

For example, in a case where the transmission mode is the distributionmode, the transmission processing circuit 12 sets continuous values asserial numbers. In a case where the transmission mode is not thedistribution mode, the transmission processing circuit 12 sets alternatevalues as serial numbers. In another example, the least significant bitof a serial number is used for the display of a transmission mode.

The media independent interface transmission block 13 addsidentification codes to the head and tail of the data transmitted fromthe transmission processing circuit 12 and transmits the data to thecorresponding physical unit 1 b. The media independent interfacetransmission block 13 performs processing without depending ontransmission media.

As illustrated in FIG. 3, the media access control unit 2 a in areceiving apparatus 2 includes two media independent interface receptionblocks 21, a reception processing circuit 22, and an upper portionreception interface 23.

The media independent interface reception block 21 receives data fromthe corresponding physical unit 2 b and transmits the data to thereception processing circuit 22. The media independent interfacereception block 21 performs processing without depending on transmissionmedia.

The reception processing circuit 22 performs reception processing basedon the reception statuses of the two media independent interfacereception blocks 21 and transmits information about a reception mode(transfer mode), received data, and a reception error (in the event of areception error) to the upper portion reception interface 23.

Specifically, in a case where the reception processing circuit 22receives distribution data from the two media independent interfacereception blocks 21, the reception processing circuit 22 performsrestoration reception processing. That is, the reception processingcircuit 22 couples #N and distribution data received from one of themedia independent interface reception blocks 21 and distribution dataand CRC received from the other one of the media independent interfacereception blocks 21 and checks #N and CRC. The reception processingcircuit 22 transmits the coupled distribution data to the upper portionreception interface 23 along with information indicating that thecurrent mode is the distribution mode. In a case where the receptionprocessing circuit 22 detects an error at the time of checking #N andCRC, the reception processing circuit 22 transmits a reception error tothe upper portion reception interface 23.

The reception processing circuit 22 determines whether distribution datahas been received based on, for example, whether serial numbers arecontinuous values or alternate values. In another example, the receptionprocessing circuit 22 determines whether distribution data has beenreceived based on the least significant bit of a serial number.

In a case where the reception processing circuit 22 receives data fromonly one of the media independent interface reception blocks 21, thereception processing circuit 22 performs nonredundant receptionprocessing. That is, the reception processing circuit 22 performs anerror check using #N and CRC included in data received from one of themedia independent interface reception blocks 21. The receptionprocessing circuit 22 removes #N and CRC from the data received from themedia independent interface reception block 21 and transmits a remainingpart of the data to the upper portion reception interface 23 as receiveddata along with information indicating that the current mode is thenonredundant mode. In a case where the reception processing circuit 22detects an error at the time of checking #N and CRC, the receptionprocessing circuit 22 transmits a reception error to the upper portionreception interface 23.

In a case where the reception processing circuit 22 receives data otherthan distribution data from the two media independent interfacereception block 21, the reception processing circuit 22 performsredundant reception processing. That is, the reception processingcircuit 22 performs an error check using #N and CRC included in datareceived from each of the media independent interface reception blocks21. In a case where at least one of the pieces of data received from themedia independent interface reception blocks 21 include no error, thereception processing circuit 22 removes #N and CRC from the dataincluding no error and transmits a remaining part of the data to theupper portion reception interface 23 as received data. At that time, thereception processing circuit 22 also transmits information indicatingthat the current mode is the redundant mode to the upper portionreception interface 23. In a case where the reception processing circuit22 detects an error at the time of checking #N and CRC, the receptionprocessing circuit 22 transmits a reception error to the upper portionreception interface 23.

In the redundant reception processing, when a case is continuouslyrepeated predetermined times where an error is not detected in pieces ofdata received from the two media independent interface reception blocks21, the reception processing circuit 22 requests the upper portion tochange the mode from the redundant mode to the distribution mode.

The upper portion reception interface 23 transmits received data,information about the reception mode (the distribution mode, thenonredundant mode, or the redundant mode), and a reception error (in theevent of a reception error in a check result) to the upper portion.

Next, a process performed by the media access control unit 1 a in thetransmission apparatus 1 and a process performed by the media accesscontrol unit 2 a in the receiving apparatus 2 will be described. FIG. 4is a flowchart illustrating a process performed by the media accesscontrol unit 1 a in the transmission apparatus 1. FIG. 5 is a flowchartillustrating a process performed by the media access control unit 2 a inthe receiving apparatus 2. FIG. 4 illustrates a process performed in acase where two lanes are available.

As illustrated in FIG. 4, the media access control unit 1 a determineswhether there is transmission data (step S1). The media access controlunit 1 a repeats the processing of step S1 until it determines thatthere is transmission data. When there is transmission data, the mediaaccess control unit 1 a determines whether the transmission mode is thedistribution mode (step S2). When the transmission mode is thedistribution mode, the media access control unit 1 a performsdistribution transmission processing (step S3). The distributiontransmission processing is processing for distributing transmission databetween two lanes.

On the other hand, when the transmission mode is not the distributionmode, the media access control unit 1 a performs duplicationtransmission processing (step S4). The duplication transmissionprocessing is processing for transmitting transmission data using bothlanes.

The media access control unit 1 a performs a serial number updating(step S5). For example, in the case of the distribution mode, the serialnumber updating is performed by setting continuous values as serialnumbers. In the case of a mode other than the distribution mode, theserial number updating is performed by setting alternate values asserial numbers.

Thus, since the media access control unit 1 a performs the duplicationtransmission processing, a data transfer may be continuously performedeven in a situation where the transmission qualities of two lanesalternately deteriorate.

As illustrated in FIG. 5, the media access control unit 2 a determineswhether there is received data (step S11). The media access control unit2 a repeats the processing of step S11 until it determines that there isreceived data. When there is received data, the media access controlunit 2 a determines whether the received data is distribution data (stepS12). For example, the media access control unit 2 a determines whetherthe received data is distribution data based on whether the serialnumbers are continuous numbers or alternate numbers.

When the received data is distribution data, the media access controlunit 2 a determines whether a waiting time for both receptions hasexpired (step S13). When the waiting time for both receptions hasexpired, the media access control unit 2 a ends the process. When thewaiting time for both receptions has not expired, the media accesscontrol unit 2 a performs restoration reception processing (step S14).

On the other hand, when the received data is not distribution data, themedia access control unit 2 a determines whether a waiting time for bothreceptions has expired (step S15). When the waiting time for bothreceptions has expired, the media access control unit 2 a performsnonredundant reception processing (step S16). On the other hand, whenthe waiting time for both receptions has not expired, the media accesscontrol unit 2 a performs redundant reception processing (step S17).

Thus, the media access control unit 2 a specifies a transfer mode andperforms reception processing based on the transfer mode. Accordingly,the transmission apparatus 1 may change a transfer mode at the time oftransmitting data.

As described above, in an embodiment, upon receiving an instruction fortransmitting data in the redundant mode, the media access control unit 1a in the transmission apparatus 1 transmits transmission data to the twophysical units 1 b without performing renegotiation with the receivingapparatus 2. The two physical units 1 b transmit the transmission datausing respective lanes. Accordingly, the suspension of a data transferbetween the transmission apparatus 1 and the receiving apparatus 2 dueto renegotiation may be suppressed. In addition, the situation where thetransmission qualities of two lanes alternately deteriorate may beaddressed.

In an embodiment, the reception processing circuit 22 performs redundantreception processing upon receiving data other than distribution datafrom the two media independent interface reception blocks 21.Accordingly, the situation where the transmission qualities of two lanesalternately deteriorate may be addressed.

In an embodiment, since the reception processing circuit 22 determineswhether received data is distribution data based on whether serialnumbers are continuous numbers or alternate numbers, the receptionprocessing circuit 22 may specify a reception mode withoutrenegotiation.

In an embodiment, when a case where is continuously repeatedpredetermined times where an error is not detected in pieces of datareceived from the two media independent interface reception blocks 21,the reception processing circuit 22 requests the upper portion to changethe mode from the redundant mode to the distribution mode. Accordingly,the upper portion of the receiving apparatus 2 may request the upperportion of the transmission apparatus 1 to change the mode from theredundant mode to the distribution mode.

In an embodiment, the transmission apparatus 1 and the receivingapparatus 2 are provided as different apparatuses. However, thetransmission apparatus 1 and the receiving apparatus 2 may be includedin a single transfer apparatus.

All examples and conditional language provided herein are intended forthe pedagogical purposes of aiding the reader in understanding theinvention and the concepts contributed by the inventor to further theart, and are not to be construed as limitations to such specificallyrecited examples and conditions, nor does the organization of suchexamples in the specification relate to a showing of the superiority andinferiority of the invention. Although one or more embodiments of thepresent invention have been described in detail, it should be understoodthat the various changes, substitutions, and alterations could be madehereto without departing from the spirit and scope of the invention.

What is claimed is:
 1. A transfer apparatus for performing transmissionand reception of data using a plurality of lanes, the transfer apparatuscomprising: a transmission control unit configured to, upon receiving atransmission instruction for performing a data transfer in a redundantmode in which the same data is transferred using a plurality of lanes,output transmission data as first data and second data withoutrenegotiation with another transfer apparatus; a first transmission unitconfigured to transmit the first data output by the transmission controlunit via a first lane; and a second transmission unit configured totransmit the second data output by the transmission control unit via asecond lane.
 2. The transfer apparatus according to claim 1, furthercomprising: a first reception unit configured to receive third datatransmitted from another transfer apparatus using the first lane; asecond reception unit configured to receive fourth data transmitted fromthe other transfer apparatus using the second lane; and a receptioncontrol unit configured to, in a case where it is determined that atleast one of the third data and the fourth data include no error,perform redundant reception processing for outputting data including noerror.
 3. The transfer apparatus according to claim 2, wherein thereception control unit performs the redundant reception processing in acase where the reception control unit determines that a current mode isthe redundant mode based on serial numbers included in the third dataand the fourth data.
 4. The transfer apparatus according to claim 2,wherein, in a case where the reception control unit continuouslydetermines a predetermined number of times that neither of the thirddata and the fourth data includes an error, the reception control unitmakes a request for changing a mode from the redundant mode to adistribution mode in which data is distributed and transmitted.
 5. Atransfer method of performing transmission and reception of data using aplurality of lanes comprising: upon receiving a transmission instructionfor performing a data transfer in a redundant mode in which the samedata is transferred using a plurality of lanes, outputting transmissiondata as first data and second data without renegotiation with anothertransfer apparatus; transmitting the output first data via a first lane;and transmitting the output second data via a second lane.